Unfortunately, the new version changed the completed date on all of my completed tasks to yesterday's date. I didn't realise this and one of the first things I did was to sync with Toodledo. Of course, this changed all of the data in Toodledo. I'm a bit peeved about this!
I had Todo set to be the authoritative source for conflict resolution so I've now changed that to Toodledo, although I am not sure if this would actually have saved my data from being altered anyway.
I am pretty sure this happened the last time I upgraded Todo although I was a new user at the time and assumed that I had done something wrong inadvertently. Now I think it is a bug.
Anyway, FWIW I've posted a complaint about this on Appigo's Google Group.
p.s. I also have Toodledo on my iPhone so I synced that after I found the problem, hoping that the completed dates on Toodledo iPhone would update Toodledo online. No such luck - the reverse happened. :(